* [RFC net-next 14/15] selftests: net: add ipxlat coverage
[not found] <20260319151230.655687-1-ralf@mandelbit.com>
@ 2026-03-19 15:12 ` Ralf Lici
0 siblings, 0 replies; only message in thread
From: Ralf Lici @ 2026-03-19 15:12 UTC (permalink / raw)
To: netdev
Cc: Daniel Gröber, Ralf Lici, Antonio Quartulli, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, Simon Horman,
Shuah Khan, linux-kernel, linux-kselftest
Add selftests for ipxlat data plane behavior and control-plane setup.
The tests build an isolated netns topology, configure ipxlat through
YNL, and exercise core traffic classes (TCP, UDP, ICMP info/error, and
fragment-related paths). This provides reproducible end-to-end coverage
for the translation pipeline and basic regression protection for future
changes.
Signed-off-by: Ralf Lici <ralf@mandelbit.com>
---
tools/testing/selftests/net/ipxlat/.gitignore | 1 +
tools/testing/selftests/net/ipxlat/Makefile | 25 ++
.../selftests/net/ipxlat/ipxlat_data.sh | 70 +++++
.../selftests/net/ipxlat/ipxlat_frag.sh | 70 +++++
.../selftests/net/ipxlat/ipxlat_icmp_err.sh | 54 ++++
.../selftests/net/ipxlat/ipxlat_lib.sh | 273 ++++++++++++++++++
.../net/ipxlat/ipxlat_udp4_zero_csum_send.c | 119 ++++++++
7 files changed, 612 insertions(+)
create mode 100644 tools/testing/selftests/net/ipxlat/.gitignore
create mode 100644 tools/testing/selftests/net/ipxlat/Makefile
create mode 100755 tools/testing/selftests/net/ipxlat/ipxlat_data.sh
create mode 100755 tools/testing/selftests/net/ipxlat/ipxlat_frag.sh
create mode 100755 tools/testing/selftests/net/ipxlat/ipxlat_icmp_err.sh
create mode 100644 tools/testing/selftests/net/ipxlat/ipxlat_lib.sh
create mode 100644 tools/testing/selftests/net/ipxlat/ipxlat_udp4_zero_csum_send.c
diff --git a/tools/testing/selftests/net/ipxlat/.gitignore b/tools/testing/selftests/net/ipxlat/.gitignore
new file mode 100644
index 000000000000..43bd01d8a84b
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/.gitignore
@@ -0,0 +1 @@
+ipxlat_udp4_zero_csum_send
diff --git a/tools/testing/selftests/net/ipxlat/Makefile b/tools/testing/selftests/net/ipxlat/Makefile
new file mode 100644
index 000000000000..cca588945e48
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/Makefile
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0
+# IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+#
+# Copyright (C) 2026- Mandelbit SRL
+# Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+#
+# Author: Antonio Quartulli <antonio@mandelbit.com>
+# Daniel Gröber <dxld@darkboxed.org>
+# Ralf Lici <ralf@mandelbit.com>
+
+TEST_PROGS := \
+ ipxlat_data.sh \
+ ipxlat_frag.sh \
+ ipxlat_icmp_err.sh \
+# end of TEST_PROGS
+
+TEST_FILES := \
+ ipxlat_lib.sh \
+# end of TEST_FILES
+
+TEST_GEN_FILES := \
+ ipxlat_udp4_zero_csum_send \
+# end of TEST_GEN_FILES
+
+include ../../lib.mk
diff --git a/tools/testing/selftests/net/ipxlat/ipxlat_data.sh b/tools/testing/selftests/net/ipxlat/ipxlat_data.sh
new file mode 100755
index 000000000000..101e0a65f0a9
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/ipxlat_data.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+#
+# Copyright (C) 2026- Mandelbit SRL
+# Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+#
+# Author: Antonio Quartulli <antonio@mandelbit.com>
+# Daniel Gröber <dxld@darkboxed.org>
+# Ralf Lici <ralf@mandelbit.com>
+
+set -o pipefail
+
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
+source "$SCRIPT_DIR/ipxlat_lib.sh"
+
+trap ipxlat_cleanup EXIT
+
+ipxlat_setup_env
+
+# Send ICMP Echo and verify we receive a reply back
+
+RET=0
+ip netns exec "$NS4" ping -c 2 -W 2 "$IPXLAT_V4_REMOTE" >/dev/null 2>&1
+check_err $? "ping 4->6 failed"
+log_test "icmp-info 4->6"
+
+RET=0
+ip netns exec "$NS6" ping -6 -c 2 -W 2 -I "$IPXLAT_V6_NS6_SRC" \
+ "$IPXLAT_V6_NS4" >/dev/null 2>&1
+check_err $? "ping 6->4 failed"
+log_test "icmp-info 6->4"
+
+# Run a TCP data transfer over the translator path
+
+RET=0
+ipxlat_run_iperf "$NS6" "$NS4" "$IPXLAT_V4_REMOTE" 5201 -n 256K
+check_err $? "tcp 4->6 failed"
+log_test "tcp 4->6"
+
+RET=0
+ipxlat_run_iperf "$NS4" "$NS6" "$IPXLAT_V6_NS4" 5201 \
+ -B "$IPXLAT_V6_NS6_SRC" -n 256K
+check_err $? "tcp 6->4 failed"
+log_test "tcp 6->4"
+
+# Run UDP traffic to verify UDP translation and delivery
+
+RET=0
+ipxlat_run_iperf "$NS6" "$NS4" "$IPXLAT_V4_REMOTE" 5202 -u -b 5M -t 1
+check_err $? "udp 4->6 failed"
+log_test "udp 4->6"
+
+RET=0
+ipxlat_run_iperf "$NS4" "$NS6" "$IPXLAT_V6_NS4" 5202 \
+ -B "$IPXLAT_V6_NS6_SRC" -u -b 5M -t 1
+check_err $? "udp 6->4 failed"
+log_test "udp 6->4"
+
+# Send one IPv4 UDP packet with checksum=0 and verify 4->6 translation.
+
+RET=0
+ipxlat_capture_pkts "$NS6" \
+ "ip6 and udp and dst host $IPXLAT_V6_REMOTE and dst port 5555" 1 3 \
+ ip netns exec "$NS4" "$SCRIPT_DIR/ipxlat_udp4_zero_csum_send" \
+ "$IPXLAT_NS4_ADDR" "$IPXLAT_V4_REMOTE" 5555
+check_err $? "udp checksum-zero 4->6 failed"
+log_test "udp checksum-zero 4->6"
+
+exit "$EXIT_STATUS"
diff --git a/tools/testing/selftests/net/ipxlat/ipxlat_frag.sh b/tools/testing/selftests/net/ipxlat/ipxlat_frag.sh
new file mode 100755
index 000000000000..26ed351cd263
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/ipxlat_frag.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+#
+# Copyright (C) 2026- Mandelbit SRL
+# Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+#
+# Author: Antonio Quartulli <antonio@mandelbit.com>
+# Daniel Gröber <dxld@darkboxed.org>
+# Ralf Lici <ralf@mandelbit.com>
+
+set -o pipefail
+
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
+source "$SCRIPT_DIR/ipxlat_lib.sh"
+
+trap ipxlat_cleanup EXIT
+
+ipxlat_setup_env
+
+# Exercise large TCP flow on 4->6 path to cover pre-fragmentation behavior
+RET=0
+ipxlat_run_iperf "$NS6" "$NS4" "$IPXLAT_V4_REMOTE" 5301 -n 8M
+check_err $? "large tcp 4->6 failed"
+log_test "large tcp 4->6"
+
+# Exercise large UDP flow on 4->6 path to cover pre-fragmentation behavior
+RET=0
+ipxlat_run_iperf "$NS6" "$NS4" "$IPXLAT_V4_REMOTE" 5302 -u -b 20M -t 2 -l 1400
+check_err $? "large udp 4->6 failed"
+log_test "large udp 4->6"
+
+# Exercise large TCP flow on 6->4 path to cover
+# fragmentation-sensitive translation
+RET=0
+ipxlat_run_iperf "$NS4" "$NS6" "$IPXLAT_V6_NS4" 5303 \
+ -B "$IPXLAT_V6_NS6_SRC" -n 8M
+check_err $? "large tcp 6->4 failed"
+log_test "large tcp 6->4"
+
+# Exercise large UDP flow on 6->4 path to cover
+# fragmentation-sensitive translation
+RET=0
+ipxlat_run_iperf "$NS4" "$NS6" "$IPXLAT_V6_NS4" 5304 \
+ -B "$IPXLAT_V6_NS6_SRC" -u -b 20M -t 2 -l 1400
+check_err $? "large udp 6->4 failed"
+log_test "large udp 6->4"
+
+# Send oversized IPv4 ICMP Echo with DF disabled (source fragmentation allowed)
+# and verify translator drops fragmented ICMPv4 input (no translated ICMPv6
+# Echo seen in NS6)
+RET=0
+ipxlat_capture_pkts "$NS6" "icmp6 and ip6[40] == 128" 0 5 \
+ ip netns exec "$NS4" bash -c \
+ "ping -M \"dont\" -s 2000 -c 1 -W 1 \"$IPXLAT_V4_REMOTE\" \
+ >/dev/null 2>&1 || test \$? -eq 1"
+check_err $? "fragmented icmp 4->6 should be dropped"
+log_test "drop fragmented icmp 4->6"
+
+# Send oversized IPv6 ICMP echo request and verify translator drops fragmented
+# ICMPv6 input (no translated ICMPv4 Echo seen in NS4)
+RET=0
+ipxlat_capture_pkts "$NS4" "icmp and icmp[0] == 8" 0 5 \
+ ip netns exec "$NS6" bash -c \
+ "ping -6 -s 2000 -c 1 -W 1 -I \"$IPXLAT_V6_NS6_SRC\" \
+ \"$IPXLAT_V6_NS4\" >/dev/null 2>&1 || test \$? -eq 1"
+check_err $? "fragmented icmp 6->4 should be dropped"
+log_test "drop fragmented icmp 6->4"
+
+exit "$EXIT_STATUS"
diff --git a/tools/testing/selftests/net/ipxlat/ipxlat_icmp_err.sh b/tools/testing/selftests/net/ipxlat/ipxlat_icmp_err.sh
new file mode 100755
index 000000000000..946584b55895
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/ipxlat_icmp_err.sh
@@ -0,0 +1,54 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+#
+# Copyright (C) 2026- Mandelbit SRL
+# Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+#
+# Author: Antonio Quartulli <antonio@mandelbit.com>
+# Daniel Gröber <dxld@darkboxed.org>
+# Ralf Lici <ralf@mandelbit.com>
+
+set -o pipefail
+
+SCRIPT_DIR=$(dirname "$(readlink -f "$0")")
+source "$SCRIPT_DIR/ipxlat_lib.sh"
+
+trap ipxlat_cleanup EXIT
+
+ipxlat_setup_env
+
+# Trigger UDP to a closed port from NS4 and capture translated
+# ICMPv4 Port Unreachable
+RET=0
+ipxlat_capture_pkts "$NS4" "icmp and icmp[0] == 3 and icmp[1] == 3" 1 3 \
+ ip netns exec "$NS4" bash -c \
+ "echo x > /dev/udp/$IPXLAT_V4_REMOTE/9 || true"
+check_err $? "icmp-error 4->6 not observed"
+log_test "icmp-error xlate 4->6"
+
+# Trigger UDP to a closed port from NS6 and capture translated
+# ICMPv6 Port Unreachable
+RET=0
+ipxlat_capture_pkts "$NS6" "icmp6 and ip6[40] == 1 and ip6[41] == 4" 1 3 \
+ ip netns exec "$NS6" bash -c \
+ "echo x > /dev/udp/$IPXLAT_V6_NS4/9 || true"
+check_err $? "icmp-error 6->4 not observed"
+log_test "icmp-error xlate 6->4"
+
+# Send oversized DF IPv4 packet and verify local ICMPv4
+# Fragmentation Needed emission
+sysctl -qw net.ipv4.conf.ipxl0.accept_local=1
+sysctl -qw net.ipv4.conf.all.rp_filter=0
+sysctl -qw net.ipv4.conf.default.rp_filter=0
+sysctl -qw net.ipv4.conf.ipxl0.rp_filter=0
+sleep 2
+RET=0
+ipxlat_capture_pkts "$NS4" "icmp and icmp[0] == 3 and icmp[1] == 4" 1 3 \
+ ip netns exec "$NS4" bash -c \
+ "ping -M \"do\" -s 1300 -c 1 -W 1 \"$IPXLAT_V4_REMOTE\" \
+ >/dev/null 2>&1 || test \$? -eq 1"
+check_err $? "icmpv4 frag-needed emission not observed"
+log_test "icmpv4 frag-needed emission"
+
+exit "$EXIT_STATUS"
diff --git a/tools/testing/selftests/net/ipxlat/ipxlat_lib.sh b/tools/testing/selftests/net/ipxlat/ipxlat_lib.sh
new file mode 100644
index 000000000000..e27683f280d4
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/ipxlat_lib.sh
@@ -0,0 +1,273 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+#
+# Copyright (C) 2026- Mandelbit SRL
+# Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+#
+# Author: Antonio Quartulli <antonio@mandelbit.com>
+# Daniel Gröber <dxld@darkboxed.org>
+# Ralf Lici <ralf@mandelbit.com>
+
+set -o pipefail
+
+IPXLAT_TEST_DIR=$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")
+source "$IPXLAT_TEST_DIR/../lib.sh"
+
+KDIR=${KDIR:-$(readlink -f "$IPXLAT_TEST_DIR/../../../../../")}
+YNL_CLI="$KDIR/tools/net/ynl/pyynl/cli.py"
+YNL_SPEC="$KDIR/Documentation/netlink/specs/ipxlat.yaml"
+IPXLAT_IPERF_TIMEOUT=${IPXLAT_IPERF_TIMEOUT:-10}
+
+IPXLAT_TRANSLATOR_DEV=ipxl0
+IPXLAT_VETH4_HOST=veth4r
+IPXLAT_VETH4_NS=veth4n
+IPXLAT_VETH6_HOST=veth6r
+IPXLAT_VETH6_NS=veth6n
+
+IPXLAT_XLAT_PREFIX6=2001:db8:100::
+IPXLAT_XLAT_PREFIX6_LEN=40
+IPXLAT_XLAT_PREFIX6_HEX=20010db8010000000000000000000000
+IPXLAT_LOWEST_IPV6_MTU=1280
+
+IPXLAT_HOST4_ADDR=198.51.100.1
+IPXLAT_HOST6_ADDR=2001:db8:1::1
+
+IPXLAT_NS4_ADDR=198.51.100.2
+IPXLAT_NS6_ADDR=2001:db8:1::2
+export IPXLAT_V4_REMOTE=192.0.2.33
+
+IPXLAT_V6_REMOTE=2001:db8:1c0:2:21::
+IPXLAT_V6_NS4=2001:db8:1c6:3364:2::
+IPXLAT_V6_NS6_SRC=2001:db8:1c0:2:2::
+
+NS4=""
+NS6=""
+
+ipxlat_ynl()
+{
+ python3 "$YNL_CLI" --spec "$YNL_SPEC" "$@"
+}
+
+ipxlat_build_dev_set_json()
+{
+ local ifindex="$1"
+
+ jq -cn \
+ --argjson ifindex "$ifindex" \
+ --arg prefix "$IPXLAT_XLAT_PREFIX6_HEX" \
+ --argjson prefix_len "$IPXLAT_XLAT_PREFIX6_LEN" \
+ --argjson lowest_ipv6_mtu "$IPXLAT_LOWEST_IPV6_MTU" \
+ '{
+ ifindex: $ifindex,
+ config: {
+ "xlat-prefix6": {
+ prefix: $prefix,
+ "prefix-len": $prefix_len
+ },
+ "lowest-ipv6-mtu": $lowest_ipv6_mtu
+ }
+ }'
+}
+
+ipxlat_require_root()
+{
+ if [[ $(id -u) -ne 0 ]]; then
+ echo "ipxlat selftests need root; skipping"
+ exit "$ksft_skip"
+ fi
+}
+
+ipxlat_require_tools()
+{
+ if [[ ! -f "$YNL_CLI" || ! -f "$YNL_SPEC" ]]; then
+ log_test_skip "ipxlat netlink spec/ynl not found"
+ exit "$ksft_skip"
+ fi
+
+ for tool in ip python3 ping iperf3 tcpdump timeout jq; do
+ require_command "$tool"
+ done
+}
+
+ipxlat_cleanup()
+{
+ cleanup_ns "${NS4:-}" "${NS6:-}" || true
+ ip link del "$IPXLAT_TRANSLATOR_DEV" 2>/dev/null || true
+ ip link del "$IPXLAT_VETH4_HOST" 2>/dev/null || true
+ ip link del "$IPXLAT_VETH6_HOST" 2>/dev/null || true
+}
+
+# Test topology:
+#
+# host namespace:
+# - owns ipxlat dev `ipxl0`
+# - has veth peers `veth4r` and `veth6r`
+# - routes IPv4 test prefix (192.0.2.0/24) to ipxl0 (v4 network steering rule)
+# - routes xlat-prefix6 prefix (2001:db8:100::/40) out to NS6 side
+# - routes mapped NS4 IPv6 identity (2001:db8:1c6:3364:2::/128) to ipxl0
+# so NS6->NS4 traffic enters 6->4 translation
+#
+# NS4:
+# - IPv4-only endpoint: 198.51.100.2/24 on veth4n
+# - default route via host 198.51.100.1 (veth4r)
+# - sends traffic to 192.0.2.33 (translated by ipxl0 to IPv6)
+#
+# NS6:
+# - IPv6 endpoint: 2001:db8:1::2/64 on veth6n
+# - also owns mapped addresses used by tests:
+# 2001:db8:1c0:2:21:: (maps to 192.0.2.33)
+# 2001:db8:1c0:2:2:: (maps to 192.0.2.2, used as explicit src
+# since we have multiple v6 addresses)
+# - route to mapped NS4 IPv6 address is pinned via host:
+# 2001:db8:1c6:3364:2::/128
+# This keeps the 6->4 test path deterministic.
+#
+# ipxlat config under test:
+# - xlat-prefix6 = 2001:db8:100::/40
+# - lowest-ipv6-mtu = 1280
+ipxlat_configure_topology()
+{
+ local ifindex
+ local dev_set_json
+
+ if ! ip link add "$IPXLAT_TRANSLATOR_DEV" type ipxlat; then
+ echo "ipxlat link kind unavailable; skipping"
+ exit "$ksft_skip"
+ fi
+ ip link set "$IPXLAT_TRANSLATOR_DEV" up
+ ifindex=$(cat /sys/class/net/"$IPXLAT_TRANSLATOR_DEV"/ifindex)
+ dev_set_json=$(ipxlat_build_dev_set_json "$ifindex")
+
+ if ! ipxlat_ynl --do dev-set --json "$dev_set_json" >/dev/null; then
+ echo "ipxlat dev-set failed"
+ exit "$ksft_fail"
+ fi
+
+ setup_ns NS4 NS6 || exit "$ksft_skip"
+
+ ip link add "$IPXLAT_VETH4_HOST" type veth peer name "$IPXLAT_VETH4_NS"
+ ip link add "$IPXLAT_VETH6_HOST" type veth peer name "$IPXLAT_VETH6_NS"
+ ip link set "$IPXLAT_VETH4_NS" netns "$NS4"
+ ip link set "$IPXLAT_VETH6_NS" netns "$NS6"
+
+ ip addr add "$IPXLAT_HOST4_ADDR/24" dev "$IPXLAT_VETH4_HOST"
+ ip -6 addr add "$IPXLAT_HOST6_ADDR/64" dev "$IPXLAT_VETH6_HOST"
+ ip link set "$IPXLAT_VETH4_HOST" up
+ ip link set "$IPXLAT_VETH6_HOST" up
+
+ ip netns exec "$NS4" ip addr add "$IPXLAT_NS4_ADDR/24" \
+ dev "$IPXLAT_VETH4_NS"
+ ip netns exec "$NS4" ip link set "$IPXLAT_VETH4_NS" up
+ ip netns exec "$NS4" ip route add default via "$IPXLAT_HOST4_ADDR"
+
+ ip netns exec "$NS6" ip -6 addr add "$IPXLAT_NS6_ADDR/64" \
+ dev "$IPXLAT_VETH6_NS"
+ ip netns exec "$NS6" ip -6 addr add "$IPXLAT_V6_REMOTE/128" \
+ dev "$IPXLAT_VETH6_NS"
+ ip netns exec "$NS6" ip -6 addr add "$IPXLAT_V6_NS6_SRC/128" \
+ dev "$IPXLAT_VETH6_NS"
+ ip netns exec "$NS6" ip link set "$IPXLAT_VETH6_NS" up
+ ip netns exec "$NS6" ip -6 route add default via "$IPXLAT_HOST6_ADDR"
+ ip netns exec "$NS6" ip -6 route replace "$IPXLAT_V6_NS4/128" \
+ via "$IPXLAT_HOST6_ADDR"
+ sleep 2
+
+ sysctl -qw net.ipv4.ip_forward=1
+ sysctl -qw net.ipv6.conf.all.forwarding=1
+
+ # 4->6 steering rule
+ ip route replace 192.0.2.0/24 dev "$IPXLAT_TRANSLATOR_DEV"
+ # Post-translation egress:
+ # IPv6 destinations in xlat-prefix6 leave toward NS6.
+ ip -6 route replace "$IPXLAT_XLAT_PREFIX6/$IPXLAT_XLAT_PREFIX6_LEN" \
+ dev "$IPXLAT_VETH6_HOST"
+ # 6->4 steering rule
+ ip -6 route replace "$IPXLAT_V6_NS4/128" dev "$IPXLAT_TRANSLATOR_DEV"
+
+ ip link set "$IPXLAT_VETH6_HOST" mtu 1280
+ ip netns exec "$NS6" ip link set "$IPXLAT_VETH6_NS" mtu 1280
+}
+
+ipxlat_setup_env()
+{
+ ipxlat_require_root
+ ipxlat_require_tools
+ ipxlat_cleanup
+
+ ipxlat_configure_topology
+}
+
+ipxlat_run_iperf()
+{
+ local srv_ns="$1"
+ local cli_ns="$2"
+ local dst="$3"
+ local port="$4"
+ local -a args=()
+ local client_rc
+ local server_rc
+ local spid
+ local idx
+
+ for ((idx = 5; idx <= $#; idx++)); do
+ args+=("${!idx}")
+ done
+
+ ip netns exec "$srv_ns" timeout "$IPXLAT_IPERF_TIMEOUT" \
+ iperf3 -s -1 -p "$port" >/dev/null 2>&1 &
+ spid=$!
+ sleep 0.2
+
+ ip netns exec "$cli_ns" timeout "$IPXLAT_IPERF_TIMEOUT" \
+ iperf3 -c "$dst" -p "$port" "${args[@]}" >/dev/null 2>&1
+
+ client_rc=$?
+ if [[ $client_rc -ne 0 ]]; then
+ kill "$spid" >/dev/null 2>&1 || true
+ fi
+
+ wait "$spid" >/dev/null 2>&1
+ server_rc=$?
+
+ ((client_rc != 0)) && return "$client_rc"
+ return "$server_rc"
+}
+
+ipxlat_capture_pkts()
+{
+ local ns="$1"
+ local filter="$2"
+ local expect_pkts="$3"
+ local timeout_s="$4"
+ local cap_goal
+ local cap_pid
+ local rc
+ local trigger_rc
+
+ shift 4
+
+ cap_goal=1
+ [[ $expect_pkts -gt 0 ]] && cap_goal=$expect_pkts
+
+ ip netns exec "$ns" timeout "$timeout_s" \
+ tcpdump -nni any -c "$cap_goal" \
+ "$filter" >/dev/null 2>&1 &
+ cap_pid=$!
+ sleep 0.2
+
+ "$@"
+ trigger_rc=$?
+ wait "$cap_pid" >/dev/null 2>&1
+ rc=$?
+
+ if [[ $trigger_rc -ne 0 ]]; then
+ return "$trigger_rc"
+ fi
+
+ if [[ $expect_pkts -eq 0 ]]; then
+ [[ $rc -eq 124 ]]
+ else
+ [[ $rc -eq 0 ]]
+ fi
+}
diff --git a/tools/testing/selftests/net/ipxlat/ipxlat_udp4_zero_csum_send.c b/tools/testing/selftests/net/ipxlat/ipxlat_udp4_zero_csum_send.c
new file mode 100644
index 000000000000..ef9f07f8d699
--- /dev/null
+++ b/tools/testing/selftests/net/ipxlat/ipxlat_udp4_zero_csum_send.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0
+/* IPXLAT - Stateless IP/ICMP Translation (SIIT) virtual device driver
+ *
+ * Copyright (C) 2026- Mandelbit SRL
+ * Copyright (C) 2026- Daniel Gröber <dxld@darkboxed.org>
+ *
+ * Author: Antonio Quartulli <antonio@mandelbit.com>
+ * Daniel Gröber <dxld@darkboxed.org>
+ * Ralf Lici <ralf@mandelbit.com>
+ */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <linux/ip.h>
+#include <linux/udp.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+static uint16_t iphdr_csum(const void *buf, size_t len)
+{
+ const uint16_t *p = buf;
+ uint32_t sum = 0;
+
+ while (len > 1) {
+ sum += *p++;
+ len -= 2;
+ }
+ if (len)
+ sum += *(const uint8_t *)p;
+
+ while (sum >> 16)
+ sum = (sum & 0xffff) + (sum >> 16);
+
+ return (uint16_t)~sum;
+}
+
+int main(int argc, char **argv)
+{
+ static const char payload[] = "ipxlat-zero-udp-csum";
+ struct sockaddr_in dst = {};
+ struct {
+ struct iphdr ip;
+ struct udphdr udp;
+ char payload[sizeof(payload)];
+ } pkt = {};
+ in_addr_t saddr, daddr;
+ unsigned long dport_ul;
+ socklen_t dst_len;
+ ssize_t n;
+ int one = 1;
+ int fd;
+
+ if (argc != 4) {
+ fprintf(stderr, "usage: %s <src4> <dst4> <dport>\n", argv[0]);
+ return 2;
+ }
+
+ if (!inet_pton(AF_INET, argv[1], &saddr) ||
+ !inet_pton(AF_INET, argv[2], &daddr)) {
+ fprintf(stderr, "invalid IPv4 address\n");
+ return 2;
+ }
+
+ errno = 0;
+ dport_ul = strtoul(argv[3], NULL, 10);
+ if (errno || dport_ul > 65535) {
+ fprintf(stderr, "invalid UDP port\n");
+ return 2;
+ }
+
+ fd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
+ if (fd < 0) {
+ perror("socket");
+ return 1;
+ }
+
+ if (setsockopt(fd, IPPROTO_IP, IP_HDRINCL, &one, sizeof(one)) < 0) {
+ perror("setsockopt(IP_HDRINCL)");
+ close(fd);
+ return 1;
+ }
+
+ pkt.ip.version = 4;
+ pkt.ip.ihl = 5;
+ pkt.ip.ttl = 64;
+ pkt.ip.protocol = IPPROTO_UDP;
+ pkt.ip.tot_len = htons(sizeof(pkt));
+ pkt.ip.id = htons(1);
+ pkt.ip.frag_off = 0;
+ pkt.ip.saddr = saddr;
+ pkt.ip.daddr = daddr;
+ pkt.ip.check = iphdr_csum(&pkt.ip, sizeof(pkt.ip));
+
+ pkt.udp.source = htons(4242);
+ pkt.udp.dest = htons((uint16_t)dport_ul);
+ pkt.udp.len = htons(sizeof(pkt.udp) + sizeof(payload));
+ pkt.udp.check = 0;
+
+ memcpy(pkt.payload, payload, sizeof(payload));
+
+ dst.sin_family = AF_INET;
+ dst.sin_port = pkt.udp.dest;
+ dst.sin_addr.s_addr = daddr;
+ dst_len = sizeof(dst);
+
+ n = sendto(fd, &pkt, sizeof(pkt), 0, (struct sockaddr *)&dst, dst_len);
+ if (n != (ssize_t)sizeof(pkt)) {
+ perror("sendto");
+ close(fd);
+ return 1;
+ }
+
+ close(fd);
+ return 0;
+}
--
2.53.0
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